Cookware pressure indicator

ABSTRACT

A microwave pressure cooker including safety interlock mechanisms. A blow vent is provided in cooker lid, and a lock bar is pivoted to cooker lid in a position to block blow vent when lock bar is resting under its own weight. Free end of lock bar includes a lock tab. Lock tab extends through slot at periphery of lid. Cooker base includes handle with a cam section ending in a lock wall. Cooker lid is placed on base in a release position and rotated to a locking position. During this rotation lock tab rides over cam section and then falls adjacent lock wall, thus sealing blow vent. After cooking cover is physically prevented from rotating back to release position by lock tab abutting lock wall. User must physically lift lock bar to unseal blow vent to ensure internal pressure is released. A spline may hold lock bar in raised position.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to co-pending Ser. No. 29/455,339 thecontents of which are included herein by reference, and is a divisionalapplication of Ser. No. 13/898,187, filed May 20, 2013.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not applicable.

BACKGROUND OF THE INVENTION

The present invention relates in general to cooking implements, andpressure cookers for food. In particular, the present invention relatesto an improved microwave pressure cooker having safety interlockfeatures, and a guard against under-pressure locking.

Pressure cookers for use in microwave ovens are known in the literature,with U.S. Pat. No. 4,796,776 to Dalquist et al. being a good example. Inpractice, however, these devices must meet various regulations forsafety including safety interlock features. The nature of thesemicrowave pressure cookers do not lend themselves to existing interlockarrangements.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a microwave pressurecooker providing safety interlock features.

Another object of the present invention is to provide a microwavepressure cooker having a positive safety lock preventing opening of thecooker without release of internal pressure.

Yet another object of the present invention is to provide a pressureindicator which also functions to prevent negative pressure within thecooker during cooling.

These and other objects are achieved by a microwave pressure cooker. Thepressure cooker includes safety interlock meeting current regulations. Ablow vent is provided in the cooker lid, and a lock bar is pivoted tothe cooker lid in a position to block the blow vent when the lock bar isresting under its own weight. The free end of the lock bar includes alock tab with a spline projecting outward. The lock tab extends througha slot at the periphery of the lid. The cooker base include a handlewith a cam section ending in a lock wall. The cooker lid is placed onthe base in a release position and rotated to a locking position. Duringthis rotation the lock tab rides over the cam section and then fallsadjacent the lock wall, thus sealing the blow vent. After cooking thecover is physically prevented from rotating back to the release positionby the lock tab abutting the lock wall. The user must physically liftthe lock bar which in turn unseals the blow vent to ensure internalpressure is released. The spline may hold the lock bar in the raisedposition during rotation to the release position.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the invention noted above are explained inmore detail with reference to the drawings, in which like referencenumerals denote like elements, and in which:

FIG. 1 is a top perspective view of a microwave pressure cookeraccording to the present invention in the locking position;

FIG. 2 is a top perspective exploded view thereof;

FIG. 3 is a bottom perspective view of the lid of the pressure cooker;

FIG. 4 is a top perspective view of the pressure cooker in the releaseposition;

FIGS. 5a-5c are detailed cross-sectional views generally along line 5-5of FIG. 1 illustrating the movements of the locking bar during lockingand release;

FIG. 6 is a detail cross-sectional view along line A-A of FIG. 1illustrating the pressure relief valve;

FIG. 7 is a detail cross-sectional view along line A-A of FIG. 1illustrating the pressure indicator; and

FIG. 8 is a top perspective view of a pressure indicator stem accordingto the present invention.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, a microwave pressure cooker according to thepresent invention is generally designated by reference numeral 10. Thecooker 10 includes a base 12 in the form of a bowl with an upperperipheral edge, and a cover 14 which is generally concave with adownwardly extending lip 16 sized to fit over the edge of the base 12.The cover and base are formed of a polymer suitable for the microwave.As seen in FIG. 2, the base 12 includes a set of spaced bayonet ledges18 extending radially outward from, and spaced peripherally about, theupper peripheral edge. Similarly, the cover 14 includes a set of matingledges 20 extending radially inward from, and spaced peripherally about,the lip 16. As is known in the art, the mating ledges 20 may passvertically between the bayonet ledges 18 only in a release position ofthe cover 14 with respect to the base 12. By rotating the cover 14 withrespect to the base from this release position the mating ledges 20 willpass below the bayonet ledges until the cover 14 reaches a lockingposition with respect to the base 12. In this locking position theinterference of the ledges 18 and 20 prevents the cover from rising withrespect to the base, and this is the operating condition of the cooker10.

As is known in the art, an annular gasket 22 is provided to seal betweenthe base 12 and cover 14. The gasket 22 preferably will be looselyretained within the lip 16 of the cover 14 to ease assembly. The cooker10 also includes a pair of base handles 24 extending radially outwardfrom diametrically opposed positions on the base 12, and a pair of coverhandles 26 extending radially outward from diametrically opposedpositions on the cover 14. These are placed such that the cover handles26 align with and overlie the base handles 24 when the cover 14 is inthe locking position. This is shown in FIG. 1.

The cover 14 includes first and second valve apertures 28 and 30,respectively, spaced from each other. The first aperture 28 will receivean elastomeric pressure relief valve 32 best illustrated in FIG. 6. Thevalve 32 takes the form of a disc sized for the first aperture 28 andhaving spaced peripheral flanges which will overly the top and bottomfaces of the cover 14 to removably secure the valve 32 to the cover 14.The valve includes a slit or slits 34 and the valve will deform underpressure within the cooker to open the slit 34 and allow steam to ventwhile maintaining a desired pressure. As may be seen, it is preferredthat the valve 32 be formed symmetrical such that either face may beinserted facing out and still operate properly.

The second aperture 30 will receive a pressure indicator valve 36. Asbest shown in FIG. 7 the indicator valve includes an elastomericindicator disc 38 secure similarly to that of relief valve 32, butincluding a central aperture 40. Received in central aperture 40 is anindicator stem 42 having an enlarged base 44 within the cooker 10, aneck 46 slidingly received within aperture 40, and a slightly enlargedhead 48 to retain the stem 42 from falling through. As is known in theart, pressure within the cooker will cause the stem 42 to rise,providing a visual indication that the cooker is under pressure.

In the preferred embodiment, both apertures 28 and 30 are of the samediameter, as are valve 32 and disc 38. This arrangement will allow theuser to place the valves 32 and 36 in either aperture 28 or 30 andprevent any incorrect assembly.

During cooling after cooking the indicator stem will eventually fall tothe position shown in FIG. 7 due to a lack of internal pressure. Whilethe neck 46 is smaller than the aperture 40, the lower end of head 48can plug aperture 40 in this rest position. With further cooling of thefood, this can cause a negative pressure situation within the cooker 10,causing it to be difficult to open. To avoid this, the lower end of head48 includes at least one channel 50 providing fluid communication withatmosphere even in the rest position of FIG. 7. The channel 50 may beformed by two or more flanges 52 extending out from the lower end of thehead 48. Alternatively, the indicator disc 38 may include channels (notshown) formed by extending ribs (not shown) about aperture 40 to allowthis fluid communication. Each of these arrangements is intended to beencompassed by the term means for permitting fluid communication toatmosphere while in the rest position.

The cooker 10 also include a safety interlock arrangement. The cover 14includes a lock bar 54 having a first end 56 hinged to the cover 14 todefine a free end 58. The first end 56 may be hinged to the cover 14 viamating projections and depressions formed on the cover 14 and lock bar54. The lock bar may thus be rotated (oscillated) upward and downwardwith respect to the cover 14. The free end 58 of the lock bar extendsbeyond lip 16 and above one of the cover handles 26. This cover handle26 includes a slot 60 extending therethrough. The free end 58 of thelock bar 54 includes a lock tab 62 extending downward therefrom andsized to be freely received through the slot 60. As best shown in FIG.4, when cover 14 is placed on base 10 in the release position the locktab 62 will be adjacent a first edge of the base handle 24.

This first edge of the base handle 24 includes an upwardly projectingcam section 64 to engage with a leading edge 66 of the lock tab 62 asthe cover 14 (and thus the lock tab 62) is rotated from the releaseposition toward the lock position. One or both of the lock tab 62 andcam section 64 are tapered to smoothly lift the lock tab (and thusrotate the entire lock bar 54) during this cover rotation. The camsection 64 also defines a lock wall 68 at its rear edge forming avertical abutment. The length of the cam section 64 is chosen so thatwhen the cover 14 is in the lock position with respect to the base 12,the lock wall 68 is closely adjacent to a trailing edge 70 (FIG. 2) ofthe lock tab 62.

The locking operation will now be described. As noted, when the cover 14is first placed on the base 12 in the release position the leading edge66 of the lock tab 62 will be adjacent to the base handle 24 and the camsection 64 on that handle. This is best shown in FIG. 4. The user thenmanually rotates the cover toward the lock position (clockwise in theembodiment shown). This will cause the lock tab 62 to lift and ride overthe cam section 64 (rotating the entire lock bar 54). This is bestillustrated in FIG. 5a . Upon continued rotation the cover 14 will reachthe lock position, at which point the lock tab 62 will reach the end ofthe cam section 64 and will drop downward under its own weight (againrotating the entire lock bar 54). In this position the trailing edge 70of the lock tab 62 will be adjacent to the lock wall 68 formed by theend of the cam section 64. This is illustrated in FIGS. 1 and 5 b.

As may be envisioned, any attempt to manually rotate the cover 14 fromthe lock position toward the release position will be physically blockedby the lock tab 62 abutting against the lock wall 68. To open the cooker10 the user must manually lift the lock bar 54 to move the lock tab 62above the height of the lock wall 68. While not required, it ispreferred to provide the lock tab 62 with a projecting spline 72positioned to hold the lock tab in such a raised position by abutmentwith the slot 60 (with the lock tab 54 elastically deforming to allowthe spline to ride over the slot 60). This is illustrated in FIG. 5c .With this arrangement the user need not hold the lock bar in the raisedposition of FIG. 5c and may instead grasp the various handles to rotatethe cover 14. Finally, the free end of the lock tab 62 may include anundercut 74 intended to abut against slot 60 to prevent the lock tab 62from falling out of the slot 60 when the user inverts the cover 14during use.

While not required it is preferred that the cover 14 also include a blowvent 76 extending therethrough at a position beneath the lock bar 54.The lock bar 54 will then include a mating plug 78 on its lower facepositioned to block the blow vent when the lock bar 54 is in the restposition. To provide an appropriate seal to ensure pressure within thecooker 10 the plug 78 may be formed as an elastomer button (as shown),or the blow vent 76 may have an elastomeric ring (not shown). Finally,the lip 16 of cover 14 may include a ring aperture 80 extendingtherethrough at a position adjacent the gasket 22. As best illustratedin FIGS. 5a-c , the ring aperture is sized to be blocked by the gasket22 during normal use.

The operation and full safety features will now be described. When thecover 14 is first placed upon the base 12 in the release position theledges 18 and 20 are not yet engaged. As such, the cover 14 may freelylift with respect to the base 12 and no pressure may be achieved in thecooker. Once the user begins to rotate the cover 14 toward the lockposition then the lock tab 62 will ride up over the cam section 64. Thiswill rotate the entire lock bar 54, thus lifting the plug 78 to open theblow vent 76. This again prevents pressure from being achieved in thecooker 10. Once the cover 14 has been rotated to the lock position thelock bar 54 will rotate downward with the lock tab 62 falling down thelock wall 68 of the cam section 64. This will cause the plug 78 to blockthe blow vent 76. At this point, with the ledges 18 and 20 fully engagedin the lock position, pressure may be achieved in the cooker 10 with arise in internal temperature due to cooking.

The microwaves will pass through the cooker 10 to heat the food andthereby raising the internal pressure within the cooker 10. As theinternal pressure rises, the indicator stem 42 will rise to provide avisual indication of proper operation to the user. The relief valve 32is designed to deform and open the slit 34 upon reaching the desiredoperating pressure, to thus vent the cooker 10 and prevent any furtherpressure increase above operating pressure. However, should theindicator valve 36 become blocked and the pressure rise appreciablyabove operating pressure, then the indicator disc 38 is designed todeform and be blown from its aperture 30 to vent the cooker 10.Similarly, should the indicator disc 38 fail to unseat, and the pressurerise even further then the relief valve 32 is similarly designed todeform and be blown from the aperture 28. This would again vent thecooker 10. Should all these measures fail, and the pressure rise yetmore, then the seal aperture 80 has been designed and sized to allow thegasket 22 to deform under pressure through the seal aperture 80 to againvent the cooker 10. Finally, should all previous measure fail and thepressure rise yet more, then the plug 78 will be lifted by the pressure(rotating the lock bar 54 upward against its own weight) to again ventthe cooker 10. It is again noted that the lock bar 54 is not held in therest position of FIG. 5b , but simply rests there under its own weightand is freely lifted by the user (or the internal pressure asdescribed).

After the food has been cooked the proper time, microwaves are no longerapplied. The food within the cooker 10 begins to cool and the internalpressure begins to reduce. The indicator stem 42 will fall when thepressure is reduced. The cooker 10 may still contain pressure, however.As noted above, rotation of the cover 14 from the lock position to therelease position is blocked by the trailing edge 70 of the lock tab 62butting against the lock wall 68. The user must first manually lift thelock tab 62, thus rotating the lock bar 54 to a position as illustratedin FIG. 5c . As shown there, this will move the plug 78 from blockingthe blow vent 76. In this manner, the cooker 10 is automatically ventedby the same operation which unlocks the cover for opening. This ventingoccurs while the cover is still in the lock position and the ledges 18and 20 are still engaged. As such, it is ensured that the cooker isvented before the cover 14 reaches the release position.

From the foregoing it will be seen that this invention is one welladapted to attain all ends and objects set forth above together with theother advantages which are inherent within its structure.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the scope of theclaims.

Since many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth of shown in the accompanying drawings is to beinterpreted as illustrative, and not in a limiting sense.

What is claimed is:
 1. A heatable container, comprising: a base; acover; an aperture in the cover; and an indicator stem provided in theaperture, wherein the indicator stem has a base, a neck and a head; andmeans is provided for permitting fluid communication to atmosphere whilein a rest position, wherein the means for permitting fluid communicationto atmosphere while in said rest position includes at least two flangesprovided on the indicator stem between the base and the head; and achannel is formed by the at least two flanges.
 2. A heatable containeras in claim 1, wherein: an indicator disc is provided in the cover, andthe aperture is in the indicator disc.
 3. A heatable container as inclaim 2, wherein: the indicator stem is movable between a raisedposition under pressure and said rest position.